Augustin Marius (Mayer) was a Catholic theologian, dean of the theological school of the University of Vienna, Austria, and in the same year cathedral preacher in Regensburg, Bavaria, Germany, which was the time when Balthasar Hubmaier resigned his pastorate there. During this period Hans Denck was also in Regensburg and had some contact with Marius (preface to Eyngelegte schrifft, p. 1, reprinted by E. Dürr and Paul Roth in Aktensammlung, 584 ff.). Marius was probably instrumental in procuring for Denck a position in the local "Stift; Denck resigned this position when he turned to Protestant doctrine (Staehelin, 428).

On 25 February 1525 Marius received a call to Freising as suffragan, but remained in Regensburg over a year longer while he raised the sum he had to pay Rome for this position. In Freising he successfully attacked "false doctrine and heresy" (according to Gropp, his first biographer). In 1526 he was called to Basel to take the position of the suffragan, who had joined the Reformed Church, "in order to help to keep the sinking Catholic religion upright" (Reininger, 117).

Like Oecolampadius and his colleague Thomas Geyerfalk, Marius and his colleague Leonard Rebhan of St. Peter were commissioned to refute the teachings of the imprisoned Anabaptist leader "Karlin N." probably Karl Brennwald, in a disputation. Oecolampadius wanted Denck also to take part in the disputation. In the entire history of the Anabaptists this is one of the few attempts to combine Catholic and Protestant forces in an effort to combat Anabaptist teaching.

Four articles were to be discussed: infant baptism, government, the oath, and discipleship (Nachfolge). The theses were drawn up by Karlin and presented to Oecolampadius and Marius shortly before the end of June 1527, as follows:

Infant baptism is an abomination before God and idolatry.

The government is instituted by God; but if the government acts contrary to the command of Christ, it is not Christian, and obedience to it is not obligatory.

The swearing of oaths is forbidden; it is not permissible for anyone to swear. For what is more than Yea and Nay is of the evil one; therefore one must not swear at all, not for any reason.

In short, he who teaches and acts contrary to Christ is a deceiver.

Before the disputation Marius declared to the council that he could not engage in debate with Karlin in the presence of Oecolampadius, since the latter was a Vreitäufer; it was known that he had permitted postponing the baptism of children until their third year (Staehelin, Briefe II, 93, note 8). Another factor may have been the decree of the pope prohibiting disputation with heretics (Anshelm, 361). Marius requested and received permission to present his refutation in writing. He later published the address he delivered before the council with his official opinion.

The disputation was not held, but Karlin explained his four theses orally to the council. The Protestant and Catholic theologians were to present their arguments within four days.

The statement made by Bullinger and later by Hottinger (Helvetische Kirchen-Geschichte III, 387), that Oecolampadius disputed with the Swiss Brethren on these questions in St. Martin's church on 10 June 1527 is an error (Staehelin, Briefe, 78).

A few days after the theologians had handed in their opinions, the council issued a mandate against the Anabaptists (6 July 1527), ordering compulsory baptism of infants, prohibiting adult baptism and religious meetings in the forests, and setting severe penalties on lodging Anabaptist preachers (Staehelin, Das Buch, No. 49). The opinions of the theologians appeared in print, Oecolampadius' on 15 August 1527 (see Basel), and Marius' three years later.

The instigation to publish Marius' refutation was made by Johann Faber, Hubmaier's opponent and Vicar General of Konstanz; he was later made court chaplain and confessor to Duke Ferdinand, and in 1529 provost at Ofen. On his journey to the Reichstag at Speyer in 1529 he visited Marius, who had moved back to Freising. The book by Marius appeared there in 1530 with the title, Eyngelegte schrifft so uff anmutung eins Ersamen Raths zu Basel wider Carlin N. widerteufer D. Augustinus Marius Thompredicant und Wichbischoff überantwortet hat; it has 44 pages (copies may be found in the state library of München, Exeg. 1179, city library of Frankfurt, Misc. var. 678, No. 1, and city library of Augsburg, Th. H. Marius 1530). Marius based his reply on the statements presented to the council by Karlin, taking them verbatim from the court records. It maintains a remarkably conciliatory tone (Blanke, Corpus Reformatorum XCIII, 122). He comments that Karlin, a "poor, deceived Anabaptist," has not correctly understood the Holy Scripture, on which he bases his doctrine, recognizing the dead letter but not the spirit, and admonishes Karlin to "lay aside his errors and to desist from his erroneous interpretation of the doctrine of Christ."

Marius sent his reply to Johann Faber on 31 March 1529 asking him to present it to Cardinal Matthias Lang of Salzburg and to Bishop Conrad von Thüngen of Würzberg, whom he was to meet at the Reichstag in Speyer (Staehelin, Briefe, 300). The latter two are known to have been very severe in their opposition to the Anabaptists; in both Würzburg and Salzburg Anabaptists had been put to death for their faith. This booklet apparently drew the primate's attention to Marius, for on 24 April 1529 Bishop Conrad of Thüngen recommended Marius to the Würzburg chapter as cathedral preacher, offering a considerable sum from his own purse toward Marius' salary (Birkner, 87). Marius was well informed on the teachings of the individual reformers, and for this reason the bishops were glad to have his service (Birkner, 110).

In May 1529 Marius entered his position as cathedral preacher, and in 1536 he was appointed suffragan of Würzburg. At the Reichstag in Augsburg in 1530 he was one of the Catholic theologians who drew up the refutation to the Confession of Augsburg.